Providing homogeneous alloys of high temperature reactive metals such as zirconium and titanium has presented problems. U.S. Pat. No. 3,565,602 issued to Konisi et al. on Feb. 23, 1971 discusses the problem of adding constituents with different melting points and includes several prior art methods of dealing with these problems. The greater the temperature difference of melting points, the more difficult these problems become. Tin, which is commonly added as an alloying constituent of zirconium alloys, is an example of a low melting point material, the introduction of which presents significant difficulties. While alloying materials are often added using master alloys, such master alloys of the zirconium and titanium have a tendency to be pyrophoric and are prone to contribute undesirable phases such as nitrides to the alloys. Further, the master alloy is still relatively low melting and the resistance heating of the electrode tends to melt the master alloy away from the arc, resulting in an inhomogeneous product. To control the amount of tin during arc melting it is common practice to contain the unalloyed tin within a tight packet of some form within the electrode.
Attempts have also been made to reduce the electrode resistance to minimize resistance heating of the electrode during melting by, for example, providing multiple welding beads longitudinally along the electrode, however, such techniques are time consuming and have not proven totally affective. U.S. Pat. No. 3,404,206, to Barth provides for the welding of a low electrical resistance metallic strip along substantially the entire length of the electrode to avoid excessive resistance-heating of the electrode and, in particular, to provide stability against warpage of the electrode during use.
U.S. Pat. No. 4,539,688, issued to Weber on Sept. 3, 1985 provides an electrode for consumable arc melting of zirconium and titanium alloys, which alloys contain a low melting point constituent. The electrode uses a low resistance spar extending substantially the length of the electrode, with the spar being substantially free of any unalloyed low melting point alloy constituent. External members containing unalloyed low melting point constituents are attached to the spar member. Generally, this patent utilizes welding of the external members to the spar (the patent/notes, however, that external members can be mechanically attached by methods other than the welding) and commercial usage of spars with welded-on segments has proven highly successful.